Semiconductor device and method for producing the same

ABSTRACT

A gate electrode is formed on a substrate via a gate insulating film. The gate insulating film includes a high dielectric constant film containing a metal, oxygen and hydrogen, and a lower barrier film formed below the high dielectric constant film and containing a metal, oxygen, silicon and nitrogen.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a semiconductor device and amethod for producing the same, in particular, a high dielectric constantfilm used for a gate insulating film.

[0002] With recent technological advance with respect to highintegration and high speed in semiconductor devices, miniaturization ofMOSFETs has been under development. When the thickness of a gateinsulating film is being reduced to achieve the miniaturization,problems such as an increase of a gate leak current due to tunnelingcurrent are caused. In order to suppress this problem, there has beenresearch on an approach to increase a physical thickness while realizinga small SiO₂ equivalent thickness (hereinafter, referred to as “EOT”) byusing gate insulating films made of high dielectric constant materialsuch as hafnium oxide (HfO₂) and zirconium oxide (ZrO₂) (hereinafter,referred to as “high-k gate insulating films”).

[0003] For example, a method for forming a conventional high-k gateinsulating film described in U.S. Pat. No. 6,013,553 is as follows.First, an oxide layer such as a SiO₂ layer is formed on a siliconsubstrate, and then a metal film made of zirconium or hafnium isdeposited on the oxide layer by sputtering or plasma CVD. Thereafter,the metal film is subjected to an oxynitridation treatment with gas suchas NO to form a high-k gate insulating film made of zirconium oxynitride(ZrO_(x)N_(y)) or hafnium oxynitride (HfO_(x)N_(y)).

[0004] However, in the conventional high-k gate insulating film, whenheat history is applied by a high temperature treatment during theproduction process, the high dielectric constant material constitutingthe gate insulating film is crystallized, so that the electricalconductivity via the resultant crystal grain boundaries or the defectlevel increases leak current. That is to say, the thermal stability ofthe conventional high-k gate insulating film is insufficient.

SUMMARY OF THE INVENTION

[0005] Therefore, with the foregoing in mind, it is an object of thepresent invention to provide a semiconductor device employing athermally stable gate insulating film having a high relative dielectricconstant.

[0006] In order to achieve the object, a semiconductor device of thepresent invention includes a gate insulating film formed on a substrate;and a gate electrode formed on the gate insulating film, and the gateinsulating film includes a high dielectric constant film containing ametal, oxygen and silicon; and a lower barrier film formed below thehigh dielectric constant film and containing the metal, oxygen, siliconand nitrogen.

[0007] According to the semiconductor of the present invention, the highdielectric constant film constituting the gate insulating film containssilicon, so that the high dielectric constant film is prevented frombeing crystallized by a high temperature treatment in the productionprocess (e.g., a heat treatment for activating impurities at about 900°C.). Therefore, in a finished semiconductor device, the high dielectricconstant film remains mostly amorphous, so that leak current can besuppressed from occurring in the high-k gate insulating film.Consequently, the thermal stability of the high-k gate insulating filmcan be improved, and therefore a semiconductor device having excellentheat resistance can be realized, and the process margin in theproduction of a semiconductor device can be increased.

[0008] According to the semiconductor of the present invention, thelower barrier film is present below the high dielectric constant film inthe gate insulating film, so that the high dielectric constant film canbe prevented from reacting with the substrate. Moreover, the lowerbarrier film contains the same metal as in the high dielectric constantfilm, so that the relative dielectric constant of the lower barrier filmcan be increased, and thus the relative dielectric constant of theentire gate insulting film can be increased.

[0009] In the semiconductor device of the present invention, it ispreferable that the gate insulating film includes an upper barrier filmformed above the high dielectric constant film, and the upper barrierfilm contains the metal, oxygen and nitrogen.

[0010] This prevents the gate electrode material and the high dielectricconstant film material from being diffused to each other. Moreover, theupper barrier film contains the same metal as in the high dielectricconstant film, so that the relative dielectric constant of the upperbarrier film can be increased, and thus the relative dielectric constantof the gate insulting film as a whole can be increased.

[0011] In the semiconductor device of the present invention, it ispreferable to satisfy

0.23≦y/(x+y)≦0.90

[0012] when the composition of the high dielectric constant film isexpressed as M_(x)Si_(y)O, where M, O and Si represent the metal, oxygenand silicon, respectively, and X>0 and y>0.

[0013] This ensures the thermal stability of the high-k gate insulatingfilm against a heat treatment at about 900° C. while keeping therelative dielectric constant of the high-k gate insulting filmsufficient.

[0014] In the semiconductor device of the present invention, it ispreferable to satisfy

0.23≦y/(x+y)≦0.30

[0015] when the composition of the high dielectric constant film isexpressed as M_(x)Si_(y)O, where M, O and Si represent the metal, oxygenand silicon, respectively, and X>0 and y>0.

[0016] This ensures the thermal stability of the high-k gate insulatingfilm against a heat treatment at about 900° C. while keeping thereliability life of the high-k gate insulting film sufficient.

[0017] In the semiconductor device of the present invention, it ispreferable to satisfy

x/(x+y)≧0.10

[0018] when the metal is hafnium or zirconium, and the composition ofthe lower barrier film is expressed as M_(x)Si_(y)ON, where M, O, Si andN represent the metal, oxygen, silicon and nitrogen, respectively, andx>0 and y>0.

[0019] This ensures that the relative dielectric constant of the lowerbarrier film can be increased.

[0020] In the semiconductor device of the present invention, the gateelectrode may be a metal gate electrode.

[0021] A first method for producing a semiconductor device of thepresent invention includes the steps of forming a high dielectricconstant film containing a metal, oxygen and a predetermine substance ona substrate; performing a heat treatment with respect to the highdielectric constant film to diffuse silicon from the side of thesubstrate into the high dielectric constant film, thereby forming asilicon-containing high dielectric constant film; and forming aconductive film for serving as a gate electrode on thesilicon-containing high dielectric constant film.

[0022] According to the first method for producing a semiconductordevice, a predetermined substance can be desorbed from the highdielectric constant film by performing a heat treatment with respect tothe high dielectric constant film containing the predeterminedsubstance, so that silicon is diffused in the high dielectric constantfilm through the thus formed vacancies and thus a silicon-containinghigh dielectric constant film can be formed. Therefore, silicon can becontained in the high dielectric constant film efficiently, and thevacancies eventually disappear, so that the silicon-containing highdielectric constant film can become dense. The silicon-containing highdielectric constant film hardly is crystallized by a high temperaturetreatment in the production process, so that the silicon-containing highdielectric constant film remains mostly amorphous after a device iscomplete. As a result, leak current can be suppressed from occurring inthe gate insulating film including the silicon-containing highdielectric constant film, that is, the high-k gate insulating film.Consequently, the thermal stability of the high-k gate insulating filmcan be improved, and therefore a semiconductor device having excellentheat resistance can be realized, and the process margin in theproduction of a semiconductor device can be increased.

[0023] In the first semiconductor method of the present invention, it ispreferable the predetermined substance is hydrogen.

[0024] This ensures that silicon can be diffused in the high dielectricconstant film.

[0025] It is preferable that the first semiconductor method includesforming an insulating film containing silicon, nitrogen and thepredetermined substance on the substrate before the step of forming thehigh dielectric constant film; and that the step of performing a heattreatment with respect to the high dielectric constant film comprisesdiffusing silicon contained in the insulating film into the highdielectric constant film, and forming a lower barrier film by diffusingthe metal contained in the high dielectric constant film into theinsulating film.

[0026] This ensures that silicon can be diffused in the high dielectricconstant film. Furthermore, the high dielectric constant film or thesilicon-containing high dielectric constant film can be prevented fromreacting with the substrate. Moreover, the lower barrier film containsthe same metal as in the silicon-containing high dielectric constantfilm, so that the relative dielectric constant of the lower barrier filmcan be increased, and thus the relative dielectric constant of the gateinsulting film as a whole can be increased.

[0027] In the first method for producing a semiconductor device, it ispreferable that the step of forming a high dielectric constant filmcomprises forming a high dielectric constant film by CVD employing asource precursor containing the metal and the predetermined substance.

[0028] Thus ensures that a high dielectric constant film containing thepredetermined substance is formed.

[0029] In the first method for producing a semiconductor device, it ispreferable that the step of forming the high dielectric constant filmincludes forming the high dielectric constant film by CVD employing asource precursor containing the metal and a source gas containing thepredetermined substance.

[0030] Thus ensures that a high dielectric constant film containing thepredetermined substance is formed.

[0031] In the first method for producing a semiconductor device, it ispreferable that the step of forming the high dielectric constant filmincludes forming the high dielectric constant film by PVD employing atarget containing the metal in an atmosphere containing thepredetermined substance.

[0032] Thus ensures that a high dielectric constant film containing thepredetermined substance is formed.

[0033] A second method for producing a semiconductor device of thepresent invention includes the steps of forming a high dielectricconstant film containing a metal, oxygen and hydrogen on a substrate;performing a heat treatment with respect to the high dielectric constantfilm to diffuse silicon from the side of the substrate into the highdielectric constant film, thereby forming a silicon-containing highdielectric constant film; and forming a conductive film for serving as agate electrode on the silicon-containing high dielectric constant film.

[0034] According to the second method for producing a semiconductordevice, hydrogen can be desorbed from the high dielectric constant filmby performing a heat treatment with respect to the high dielectricconstant film containing hydrogen, so that silicon is diffused in thehigh dielectric constant film through the thus formed vacancies and thusa silicon-containing high dielectric constant film can be formed.Therefore, silicon can be contained in the high dielectric constant filmefficiently, and the vacancies eventually disappear, so that thesilicon-containing high dielectric constant film can become dense. Thesilicon-containing high dielectric constant film hardly is crystallizedby a high temperature treatment in the production process, so that thesilicon-containing high dielectric constant film remains mostlyamorphous after a device is complete. As a result, leak current can besuppressed from occurring in the gate insulating film including thesilicon-containing high dielectric constant film, that is, the high-kgate insulating film. Consequently, the thermal stability of the high-kgate insulating film can be improved, and therefore a semiconductordevice having excellent heat resistance can be realized, and the processmargin in the production of a semiconductor device can be increased.

[0035] It is preferable that the second method for producing asemiconductor device includes forming an insulating film containingsilicon, nitrogen and hydrogen on the substrate before the step offorming the high dielectric constant film; and that the step ofperforming a heat treatment with respect to the high dielectric constantfilm includes diffusing silicon contained in the insulating film intothe high dielectric constant film, and forming a lower barrier film bydiffusing the metal contained in the high dielectric constant film intothe insulating film.

[0036] This ensures that silicon can be diffused in the high dielectricconstant film. Furthermore, the high dielectric constant film or thesilicon-containing high dielectric constant film can be prevented fromreacting with the substrate. Moreover, the lower barrier film containsthe same metal as in the silicon-containing high dielectric constantfilm, so that the relative dielectric constant of the lower barrier filmcan be increased, and thus the relative dielectric constant of theentire gate insulting film can be increased.

[0037] In the second method for producing a semiconductor device, it ispreferable that the step of forming the high dielectric constant filmincludes forming the high dielectric constant film by CVD employing asource precursor containing the metal and hydrogen.

[0038] Thus ensures that a high dielectric constant film containinghydrogen can be formed.

[0039] In the second method for producing a semiconductor device, it ispreferable that the step of forming the high dielectric constant filmincludes forming the high dielectric constant film by CVD employing asource precursor containing the metal and a source gas containinghydrogen.

[0040] Thus ensures that a high dielectric constant film containinghydrogen can be formed.

[0041] In the second method for producing a semiconductor device, it ispreferable that the step of forming the high dielectric constant filmincludes forming the high dielectric constant film by PVD employing atarget containing the metal in an atmosphere containing hydrogen.

[0042] Thus ensures that a high dielectric constant film containinghydrogen can be formed.

[0043] In the first or the method for producing a semiconductor device,it is preferable that the metal is hafnium or zirconium.

[0044] This ensures that the relative dielectric constant of thesilicon-containing high dielectric constant film can be increased.

[0045] In the first or the second method for producing a semiconductordevice, it is preferable that the method includes the step of forming anupper barrier by nitriding a surface of the silicon-containing highdielectric constant film between the step of performing a heat treatmentwith respect to the high dielectric constant film and the step offorming a conductive film.

[0046] This prevents the gate electrode material and the high dielectricconstant film material from being diffused to each other. Moreover, theupper barrier film contains the same metal as in the high dielectricconstant film, so that the relative dielectric constant of the upperbarrier film can be increased, and thus the relative dielectric constantof the entire gate insulting film can be increased.

[0047] In the first or the second method for producing a semiconductordevice, it is preferable that the method includes the step of forming anupper barrier by nitriding a surface of the high dielectric constantfilm between the step of forming a high dielectric constant film and thestep of performing a heat treatment with respect to the high dielectricconstant film.

[0048] This prevents the gate electrode material and the high dielectricconstant film material from being diffused to each other. Moreover, theupper barrier film contains the same metal as in the high dielectricconstant film, so that the relative dielectric constant of the upperbarrier film can be increased, and thus the relative dielectric constantof the entire gate insulting film can be increased.

[0049] In the first or the second method for producing a semiconductordevice, it is preferable that the temperature for the heat treatment inthe step of performing the heat treatment with respect to the highdielectric constant film is 600° C. or more and 850° C. or less.

[0050] This ensures that the predetermined substance or hydrogen can bedesorbed from the high dielectric constant film, and that silicon can bediffused in the high dielectric constant film.

[0051] In the first or the second method for producing a semiconductordevice, it is preferable to satisfy T≦6.69·y/(x+y)+749.4, when thecomposition of the silicon-containing high dielectric constant film isexpressed as M_(x)Si_(y)O, where M, O and Si represent the metal, oxygenand silicon, respectively, and x>0 and y>0, and the maximum temperaturein the production process is expressed as T [° C.].

[0052] This ensures the thermal stability of the high-k gate insulatingfilm having the silicon-containing high dielectric constant film.

[0053] In this case, it is preferable that the gate electrode is made ofa material containing silicon, and y/(x+y)≦0.30 is satisfied.

[0054] This enables a sufficient reliability life for the high-k gateinsulating film having the silicon-containing high dielectric constantfilm.

[0055] In the first or the second method for producing a semiconductordevice, it is preferable that the gate electrode is a metal gateelectrode, and the method includes the step of performing a heattreatment with respect to the substrate after the step of forming aconductive film.

[0056] This allows the defects in the high-k gate insulating film havingthe silicon-containing high dielectric constant film to be reducedfurther.

BRIEF DESCRIPTION OF THE DRAWINGS

[0057]FIG. 1 is a cross-sectional view of a semiconductor deviceaccording to a first embodiment of the present invention.

[0058]FIG. 2 is a graph showing the relationship between the amount ofSi added to HfO₂ and the crystallization temperature of HfO₂ and thetemperature that guarantees thermal stability of HfO₂.

[0059]FIG. 3 is a diagram showing the allowable range of the compositionof Hf silicate that can maintain the thermal stability obtainedcorresponding to various maximum process temperatures.

[0060]FIG. 4 is a graph showing the relationship between the amount ofSi added to a HfO₂ film and the relative dielectric constant of the HfO₂film.

[0061]FIG. 5 is a graph showing the relationship between the amount ofSi added to a HfO₂ film and the reliability life of the HfO₂ film.

[0062]FIG. 6 is a graph showing the relationship between the amount ofSi added to a HfO₂ film and the thermal stability and the reliability ofthe HfO₂ film.

[0063]FIGS. 7A to 7C are cross-sectional views showing the processes ina method for producing a semiconductor device according to a secondembodiment of the present invention.

[0064]FIGS. 8A to 8C are cross-sectional views showing the processes ina method for producing the semiconductor device according to the secondembodiment of the present invention.

[0065]FIGS. 9A to 9D are views illustrating the behavior resulted fromPDA in the method for producing the semiconductor device according tothe second embodiment of the present invention.

[0066]FIG. 10 is a graph showing the results of measurement by TDSregarding hydrogen being desorbing from the HfO₂ film due to a heattreatment.

[0067]FIG. 11 is a graph showing the results of C-V measurement after aheat treatment with respect to a H-containing HfO₂ film formed by CVDusing Hf-t-butoxide in the method for producing a semiconductor deviceaccording to the second embodiment of the present invention.

[0068]FIG. 12 is a graph showing the result of C-V measurement after aheat treatment with respect to a H-free HfO₂ film formed by CVD using asource that does not contain hydrogen as a comparative example.

[0069]FIG. 13 is a graph showing the results of a comparison in thethermal stability between the case where the H-containing HfO₂ film (thesecond embodiment of the present invention) is used and the case wherethe H-free HfO₂ film (comparative example) is used in a MOS capacitorhaving a layered structure of Si substrate/SiN film/HfO₂film/polysilicon film.

[0070]FIG. 14 is a graph showing the relationship between the physicalthickness of a HfO₂ film that has just formed and the leak current aftera MOS capacitor is complete in the case where PDA in the method forproducing a semiconductor device of the second embodiment of the presentinvention is performed with respect to the HfO₂ film, which is aninsulating film of the MOS capacitor.

DETAILED DESCRIPTION OF THE INVENTION

[0071] First Embodiment

[0072] Hereinafter, a semiconductor device of a first embodiment of thepresent invention, more specifically, a MISFET will be described withreference to the accompanying drawings.

[0073]FIG. 1 shows the cross-sectional structure of a semiconductordevice of a first embodiment.

[0074] As shown in FIG. 1, a gate electrode 12 is formed on a siliconsubstrate 10 via a gate insulating film 11. An impurity diffusion layer13 serving as a source region or a drain region is formed on both sidesof the gate electrode 12 in the silicon substrate 10. The gateinsulating film 11 includes a high dielectric constant film ha made ofinsulative metal oxide, a lower barrier film 11 b formed below the highdielectric constant film 11 a, and an upper barrier film 11 c formedabove the high dielectric constant film 11 a.

[0075] More specifically, the high dielectric constant film 11 a isformed of a substance in which silicon is contained in hafnium oxide(HfO₂) having a high relative dielectric constant, that is, asilicon-containing hafnium oxide (Hf_(x)Si_(y)O₂, where x>y>0). Thelower barrier film lib for preventing a reaction between the siliconsubstrate 10 and the high dielectric constant film 11 a is made of, forexample, a silicon oxynitride film containing hafnium. The upper barrierfilm 11 c for preventing a reaction between the high dielectric constantfilm 11 a and the gate electrode 12 is made of, for example, asilicon-containing hafnium oxide film containing nitrogen. That is tosay, the lower barrier film 11 b and the upper barrier film 11 c arehigh dielectric constant barrier films. The gate electrode 12 is madeof, for example, a polysilicon film doped with phosphorus.

[0076] The high dielectric constant film 11 a may contain nitrogen. Whenthe physical thickness of the gate insulating film 11 is about 4 nm, thephysical thickness of the high dielectric constant film 11 a is about 2nm, the physical thickness of the lower barrier film 11 b is slightlysmaller than 1 nm, and the physical thickness of the upper barrier film11 c is slightly larger than 1 nm. All of the high dielectric constantfilm 1 a, the lower barrier film 11 b, and the upper barrier film 11 care amorphous.

[0077] In this embodiment, silicon is contained in the HfO₂ film thatserves as the high dielectric constant film 11 a for the purpose ofensuring the thermal stability of the high dielectric constant film 11a. In other words, the high dielectric constant film 11 a containingsilicon is hardly crystallized (or is only partially crystallized andremains amorphous) when being subjected to a heat treatment at a hightemperature, so that an increase of leak current due to crystal grainboundaries or defect level can be suppressed. Hereinafter, thisembodiment will be described more specifically with reference to theaccompanying drawings.

[0078]FIG. 2 shows the relationship between the amount of silicon (Si)added to HfO₂ and the crystallization temperature of HfO₂ and thethermal stability guarantee temperature of HfO₂. The crystallizationtemperature refers to the temperature at which an amorphous statestarted to change into a crystalline state. In other words, since achange of the state starts at the crystallization temperature, theentire substance (HfO₂) is not necessarily crystallized immediately evenif the temperature exceeds the crystallization temperature.

[0079] In FIG. 2, the horizontal axis shows the ratio X₁ (%representation) of the number of Si atoms contained in HfO₂ per unitvolume (hereinafter, referred to as “Si concentration”) to the sum ofthe Si concentration and the number of Hf atoms contained in HfO₂ perunit volume (hereinafter, referred to as “Hf concentration”). In otherwords, the far left end in the horizontal axis (X₁=(Si concentration/(Siconcentration+Hf concentration))×100=0%) indicates HfO₂ that contains noSi, and the far right end in the horizontal axis (X₁=(Siconcentration/(Si concentration+Hf concentration))×100=100%) indicatesSiO₂ that contains no Hf. The vertical axis shows the temperature.

[0080] As shown in FIG. 2, the crystallization temperature and thethermal stability guarantee temperature of HfO₂ increase with the ratioX₁, that is, the amount of added Si. In other words, the addition ofsilicon to HfO₂ increases the thermal stability of HfO₂. This is becausean increase of the Si amount makes it easy that Si-containing HfO₂, thatis, a Hf silicate material remains amorphous, and as a result, theentire HfO₂ film hardly is crystallized and remains amorphous.

[0081] Herein, the thermal stability guarantee temperature refers to theannealing temperature at which a drastic increase of leak current startsto occur in an insulating film made of HfO₂ when an annealing treatmentis performed with respect to a MOS capacitor structure having theinsulating film for 30 seconds in N₂ gas at 1 atm with a rapid thermalprocess (TP) apparatus. Therefore, at temperatures below the thermalstability guarantee temperature, the leak current and the capacitance inthe MOS capacitor structure employing the Si-containing HfO₂ filmindicates an ideal value. On the other hand, at temperatures above thethermal stability guarantee temperature, the leak current in the MOScapacitor structure increases by about three orders due to a drasticincrease of defects locally occurring in the Si-containing HfO₂ film. Atthis point, the capacitance in an accumulation state in a C-V(capacitance-voltage) measurement diverges, and therefore it becomesimpossible to measure the capacitance of the MOS capacitor. In otherwords, at temperatures above the thermal stability guaranteetemperature,the MOS capacitor structure employing the Si-containing HfO₂ film cannotserve as a capacitor.

[0082] When the ratio X₁ is 70% or more, the substantially entireSi-containing HfO₂ film can be kept amorphous even at high temperatures,so that even if the film is subjected to a high temperature process at1200° C., leak current can be suppressed. If the ratio X₁ is at least23%, the crystals produced when the Si-containing HfO₂ film iscrystallized are microcrystalline, and the film as a whole ispreominantly in the amorphous state. Therefore, leak current can besuppressed even if the film is subjected to a high temperature processof 900° C. Herein, the case where the material to be used is mostlyamorphous, or the case where the material to be used containscrystallites to the extent that makes substantially no influence on thethermal stability, that is, the heat resistance, is also regarded asbeing amorphous.

[0083] As shown in FIG. 2, the straight line showing the range of theprocess temperature that can be used in the process for producing asemiconductor device and the range of the Si concentration in theSi-containing HfO₂ film can be defined as T=6.69 X₁+749.4, where X₁represents the Si concentration/(Si concentration+Hf concentration)×100and T [° C.] represents the thermal stability guarantee temperature(more specifically, when a polysilicon electrode is used). In otherwords, it is necessary that the process temperature and the Siconcentration are in the range below T=6.69·X₁+749.4. More specifically,when the value of X₁, that is, the composition of the Si-containing HfO₂is determined, the process temperature has to be in the temperaturerange of not more than the thermal stability guarantee temperature Tcorresponding to the predetermined value of X₁. On the other hand, whenthe maximum temperature of the process is determined, it is necessary toselect a Si-containing HfO₂ film, that is, a Hf silicate film to whichSi is added such that X₁ is larger than a value of X₁ when the maximumtemperature is used as the thermal stability guarantee temperature T. Inthe case of the structure of the semiconductor device of this embodimentshown in FIG. 1, the Si concentration can be determined as describedabove, with respect to, for example, either the entire gate insulatingfilm 11 or a region about 2 nm below the interface with the gateelectrode 12 in the gate insulating film 11 in view of a contact withthe gate electrode 12.

[0084]FIG. 3 shows the allowable range of the composition (X₁) of Hfsilicate that can ensure the thermal stability, which was obtainedcorresponding to various maximum process temperatures based on therelationship (experiment results) shown in FIG. 2. As shown in FIG. 3,for example, when the maximum process temperature is about 900° C.(e.g., in the process in which polysilicon is used as the electrodematerial), X₁ should be at least 23% in order to prevent a drasticincrease of leak current due to defects or the like and ensures thethermal stability.

[0085]FIG. 4 shows the relationship between the amount of Si added tothe HfO₂ film and the relative dielectric constant of the HfO₂ film. InFIG. 4, the upper horizontal axis shows X₁=(Si concentration/(Siconcentration+Hf concentration))×100 as described above, which indicatesthe Si amount. The lower horizontal axis shows X₂=(Hf concentration/(Siconcentration+Hf concentration))×100 as described above, which indicatesthe Hf amount. The vertical axis shows the relative dielectric constantof the HfO₂ film. □ shows the value obtained by an actual measurement ofthe relative dielectric constant.

[0086] As shown in FIG. 4, when X₁ is 0% (that is, when the film is theHfO₂ film, which contains no Si), the relative dielectric constant ofthe HfO₂ film is about 24, which is the maximum. The relative dielectricconstant decreases as the Si amount in the HfO₂ film increases, but therelative dielectric constant is substantially constantly about 11 whenX₁ is between 30% and 90%. When the Si amount in the HfO₂ film furtherincreases and exceeds 90%, the relative dielectric constant graduallydecreases again, and the relative dielectric constant is about 3.9 whenX₁ is 100%/o (that is, when the film is the SiO₂ film, which contains noHf). Therefore, when X₁ is 90% or less, that is, when X₂ is 10% or more,a Hf silicate film having a comparatively high and stable relativedielectric constant can be realized.

[0087] According to the results shown in FIGS. 2 to 4 described above,it is important to set X₁=(Si concentration/(Si concentration+Hfconcentration))×100 in the high dielectric constant film 11 a made ofsilicon-containing HfO₂ to 23% or more and 90% or less in order that thehigh dielectric constant film 11 a (which may be a stacked structure ofa combination of the high dielectric constant film 11 a, the lowerbarrier film 11 b and/or the upper barrier film 11 c, instead of thehigh dielectric constant film 11 a) has the thermal stability whilehaving a high relative dielectric constant.

[0088] X₁=(Si concentration/(Si concentration+Hf concentration))×100 hasthe same meaning as (y/(x+y))×100 when the composition of the highdielectric constant 11 a is represented as Hf_(x)Si_(y)O (where x>0, andy>0). Similarly, X₂=(Hf concentration/(Si concentration+Hfconcentration))×100 has the same meaning as (x/(x+y))×100. X₁ and X₂show the relationship between the Si concentration and the Hfconcentration, so that also when Hf silicate to be used contains N inthe form of Hf silicate nitride, or when it contains other elements suchas Cl, F and H, the above description employing X₁ and X₂ is effective.

[0089]FIG. 5 shows the relationship between the amount of Si added tothe HfO₂ film and the reliability life of the HfO₂ film (period of timeuntil breakdown occurs). In FIG. 5, the upper horizontal axis showsX₁=(Si concentration/(Si concentration+Hf concentration))×100 asdescribed above, which indicates the Si amount. The lower horizontalaxis shows X₂=(Hf concentration/(Si concentration+Hf concentration))×100as described above, which indicates the Hf amount. The vertical axisshows the reliability life of the HfO₂ film. □ shows the value obtainedby an actual measurement of the reliability life.

[0090] More specifically, various samples of MOS capacitors having Hfsilicate films having different compositions are prepared, and a TDDB(time dependent dielectric breakdown measurement) test is performed toestimate the long term reliability life of the Hf silicate films underthe conditions of an incidence of failure of 100 ppm, an insulating filmarea (MOS area) of 0.1 cm², a temperature of 100° C., an applied voltageV_(G)=−1V, and EOT (SiO₂ equivalent thickness)=1.5 nm. The results areshown in FIG. 5. Herein, the composition of the Hf silicate in eachsample varies in the range from SiO₂, which contains no Hf to HfO₂,which contains no Si. Each sample is formed on a p-type substrate, and aconstant negative stress voltage is applied to the electrodes, setting 0V on the substrate side.

[0091] More specifically, the insulating film area of each sample usedin the IDDB test is in the range from 3×10 cm² to 5×10-5 cm². To obtainthe reliability life at an insulating film area of 0.1 cm², thefollowing equation based on the assumption that defects in theinsulating film are distributed according to the Poisson distributionwas used:

[0092] The reliability life of the insulating film area 1=thereliability life of the insulating film area 2×(insulating film area2/insulating film area 1) ^((1/β)), where β is a Weibull gradient. Thetemperature during the TDDB test is in the range from room temperatureto 1001° C. To obtain the reliability life at a temperature of 100° C.,activation energy of the reliability life obtained in advance withrespect to a temperature change was used. To obtain the reliability lifeat an incidence of failure of 100 ppm, a Weibull gradient 3 was obtainedbased on a Weibull plot obtained by the TDDB test, and then theapproximate straight line of an intrinsic breakdown was extended.Furthermore, in the TDDB test, V_(G) larger than 1 V as an absolutevalue is used, whereas in order to obtain the reliability life atV_(G)=−1 V, experiment data of the reliability life corresponding to areal electric field Eox (real) that is obtained from an equation of(V_(G) (at the time of the TDDB test)−Vfb)/Tph, where Vfb is a flat bandvoltage, and Tph is the physical thickness of the entire insulatingfilm, were extended by the straight-line approximation.

[0093] According to the results shown in FIG. 5 obtained using theabove-described method, when X₁ (upper horizontal axis) is 30% or less,that is, when X₂ is 70% or more, the reliability life of the Hf silicatefilm is 10 years or more. The results shown in FIG. 5 are those obtainedby estimating the reliability life on the lower voltage side withrespect to the real electric field Eox (real). The results obtained byestimating the reliability life on the lower voltage side with respectto the V_(G) itself at the time of the TDDB test or the effectiveelectric field Eox (effective) obtained by an equation of (V_(G) (at thetime of TDDB test)-Vfb)/EOT exhibit the similar tendency.

[0094] According to the results shown in FIGS. 2 to 4, when thermalstability and a high relative dielectric constant are targeted, it ispreferable to set X₁=(Si concentration/(Si concentration+Hfconcentration))×100 to 23% or more and 90% or less. On the other hand,according to the results shown in FIG. 5, when X₁ is 30% or less, thereliability life of 10 years or more can be obtained. That is to say,when reliability as well as thermal stability and a high relativedielectric constant are targeted, the preferable range of X₁ is 23% ormore and 30% or less. However, in the case of a process that does notrequire a high temperature treatment after a gate insulating film isformed, such as a replacement gate process (process that allows a gateelectrode to be formed after formation of source and drain regions byusing a dummy gate), more specifically, in the case of a process thatdoes not require a heat treatment at 750° C. or more after a gateelectrode is formed, it is sufficient to target only reliability, sothat the preferable range of X₁ is 30% or less.

[0095]FIG. 6 shows the relationship between the amount of Si added tothe HfO₂ film and the thermal stability and the reliability of the HfO₂film.

[0096] As shown in FIG. 6, the preferable range of the structure(composition) of the high-k gate insulating film made of a HfO₂ filmcontaining Si or the process temperature can be divided roughly intothree regions. To be specific, when only thermal stability is targeted,the preferable range is below T=6.69·X₁+749.4. In order to obtain acomparatively high relative dielectric constant in the maximum processtemperature of 900° C. as well, X₁ has to be set to 23% or more and 90%or less. In the case of a process that does not require a hightemperature treatment after a gate insulating film is formed, such as acase using a replacement gate, it is sufficient to target onlyreliability, so that it is sufficient to set X₁ to 30% or less.Furthermore, in a conventional Si process, when a high-k material isused as the gate insulating film material instead of SiON, and Poly-Sior SiGe or the like is used as the gate electrode material, that is,when annealing for activating impurities is performed at a comparativelyhigh temperature after a gate insulating film is formed, it is necessaryto target both thermal stability and reliability, so that the range thatis below T=6.69·X₁+749.4 and satisfies that X₁ is 30% or less ispreferable. In this case, when the maximum process temperature is 900°C., X₁ has to be set to 23% or more and 30% or less. It should be notedthat 900° C. is a typical temperature in annealing for activatingimpurities contained in a source region, a drain region or an electrode.

[0097] As described above, according to the first embodiment, the highdielectric constant film 11 a included in the gate insulating film 11 isa HfO₂ film containing silicon, so that the high electric constant film11 a can be prevented from being crystallized by a high temperaturetreatment in the production process. Therefore, in a finishedsemiconductor device, the high dielectric constant film 11 a remainsmostly amorphous, so that leak current can be suppressed from occurringin the gate insulating film 11, that is, the high-k gate insulatingfilm. Consequently, the thermal stability of the gate insulating film 11can be improved, so that a semiconductor device having excellent heatresistance can be realized, and the process margin in the production ofthe semiconductor device can be increased.

[0098] Furthermore, according to the first embodiment, the lower barrierfilm 11 b containing silicon, nitrogen and oxygen is present below thehigh dielectric constant film 11 a in the gate insulating film 11, sothat the high dielectric constant film 11 a and the silicon substrate 10can be prevented from being reacted with each other. Herein, the lowerbarrier film 11 b prevents the silicon substrate 10 from being oxidizedby oxygen in the high dielectric constant film 11 a. That is to say,when an oxide film having a relative dielectric constant substantiallyequal to that of a SiO₂ film is formed on the surface of the siliconsubstrate 10 as an interface layer, the relative dielectric constant ofthe gate insulating film 11 as a whole decreases significantly, andtherefore the lower barrier film 11 b is provided.

[0099] Furthermore, according to the first embodiment, the lower barrierfilm 11 b contains the same metal as in the high dielectric constantfilm 11 a, specifically, hafnium, so that the relative dielectricconstant of the lower barrier film 11 b can be higher than that of aregular silicon oxynitride film, so that the relative dielectricconstant of the gate insulating film 11 as a whole can be made higher.More specifically, as shown in FIG. 4, when hafnium is introduced intothe lower barrier film 11 b in a ratio of 10% or more with respect tosilicon (that is X₂≧10%), so that the relative dielectric constant ofthe lower barrier film 11 b can increase effectively. On the other hand,as shown in FIG. 4, when the silicon content in the lower barrier film11 b is too large (more specifically, X₁≧90%), the relative dielectricconstant decreases drastically. In other words, it is very effective toset the Hf concentration in the lower barrier film 11 b to be higherthan X₂=0% even to a slight extent in order to reduce the EOT of theentire gate insulating film 11.

[0100] Furthermore, according to the first embodiment, the upper barrierfilm 11 c is present in a portion above the high dielectric constantfilm 11 a in the gate insulating film 11, so that the material of thegate electrode 12 (polysilicon in this embodiment) is prevented frombeing mixed with the material of the high dielectric constant film 11 a(e.g., hafnium) more than necessary, and thus a reduction of therelative dielectric constant of the gate insulating film 11 can besuppressed. In this case, the barrier effect of the upper barrier film11 c can be improved by allowing the upper barrier film 11 c to containnitrogen. The relative dielectric constant of the upper barrier film 11c can be increased by allowing the upper barrier film 11 c to containthe same metal, hafnium, as the high dielectric constant film 11 a, andthus the relative dielectric constant of the entire gate insulating film11 can be increased.

[0101] In the first embodiment, it is preferable to set X₁=(Siconcentration/(Si concentration+Hf concentration))×100 in the highdielectric constant film Ha (which may be a stacked structure of acombination of the high dielectric constant film 11 a, the lower barrierfilm 11 b and/or the upper barrier film 11 c, instead of the highdielectric constant film 11 a) to 23% or more and 90% or less. By doingthis, the relative dielectric constant of the high dielectric constantfilm 11 a can be increased and even if a heat treatment at about 900° C.is performed, the high dielectric constant film 11 a can be suppressedfrom being crystallized, so that an increase of leak current due todefects or the like can be prevented. In other words, the thermalstability of the gate insulating film 11 can be ensured while therelative dielectric constant of the gate insulating film 11 is keptsufficient. In this case, it is more preferable to set X₁ in the highdielectric constant film 11 a to 23% or more and 30% or less. By doingthis, in addition to the above-described advantages, a sufficientreliability life of the high dielectric constant film 11 a, that is, thegate insulating film 11 can be obtained. When the maximum processtemperature is reduced to be significantly low by the use of areplacement gate or the like, merely setting X₁ to 30% or less ensuresthe thermal stability of the gate insulating film 11 while ensuringsufficient relative dielectric constant and reliability life of the gateinsulating film 11.

[0102] In the first embodiment, HfO₂ is used as the high dielectricconstant material included in the gate insulating film 11, but insteadof this material, ZrO₂, TiO₂, Ta₂O₅, La₂O₃, CeO₂, Al₂O₃, or BST (bariumstrontium titanium oxide) or the like can be used. Alternatively,ternary oxide such as Hf_(x)Al_(y)O₂, where x>0, and y>0) can be used.Alternatively, metal silicate in which Si atoms are contained in theabove-listed metal oxides can be used.

[0103] In the first embodiment, the lower barrier film 11 b and theupper barrier film 11 c are provided, but there may be no need ofproviding the lower barrier film 11 b and/or the upper barrier film 11c, depending on the selection of the material of the gate electrode 12.

[0104] In the first embodiment, a polysilicon electrode is used as thegate electrode 12, but instead of this, a so-called metal gate electrodemade of a metal film such as a stacked film of a TiN film and a Al film(TiN film as the lower film), a Ta film, a TiN film or a TaN film can beused. If a metal film such as a TiN film or TaN film is used as themetal gate electrode material, Si or Ge can be mixed with the metalfilm.

[0105] Second Embodiment

[0106] Hereinafter, a method for producing a semiconductor device of asecond embodiment of the present invention, specifically, a method forproducing a MISFET will be described with reference to the accompanyingdrawings.

[0107]FIGS. 7A to 7C and 8A to 8C are cross-sectional views showing theprocesses of a method for producing a semiconductor device of the secondembodiment.

[0108] First, as shown in FIG. 7A, an insulating film for isolation (notshown) is formed on a p-type silicon (100) substrate 20, and a deviceforming region is segmented. Then, standard RCA cleaning and diluted HFcleaning are performed with respect to the surface of the siliconsubstrate 20. Thereafter, a silicon nitride film (Si₃N₄ film) 21A havinga thickness of about 0.7 nm is formed on the silicon substrate 20 withNH₃ gas at a temperature of about 700° C. In this process, sufficienthydrogen is captured in the Si₃N₄ film 21A. The Si₃N₄ film 21Aeventually becomes the lower barrier film 21 (see FIG. 7C).

[0109] Next, as shown in FIG. 7B, a hafnium oxide (HfO₂) film 22A havinga thickness of about 5 nm is formed on the silicon substrate 20 by CVD(chemical vapor deposition) employing a source precursor containinghafnium. More specifically, nitrogen (N₂) gas as a carrier gas isallowed to pass through Hf-t-butoxide (C₁₆H₃₆HfO₄), which is a liquid Hfsource, to bubble the Hf-t-butoxide to evaporate the Hf-t-butoxide.Then, a RTCVD (rapid thermal CVD) treatment is performed at atemperature of about 500° C. while the N₂ gas containing the evaporatedHf-t-butoxide and dry oxygen (O₂) gas as an oxidizing agent are suppliedto a chamber in which the silicon substrate 20 (wafer) is placed, andthus a HfO₂ film 22A is formed.

[0110] In this process, the Si₃N₄ film 21A is oxidized by the O₂ gas asan oxidizing agent, and turns into a SiON film 21B. The SiON film 21Bhas barrier properties for preventing a reaction between the siliconsubstrate 20 and the HfO₂ film 22A and contains sufficient hydrogen. Inthis embodiment, after the Si₃N₄ film 21A is formed on the siliconsubstrate 20, the Si₃N₄ film 21A is oxidized during the formation of theHfO₂ film 22A to form the SiON film 21B. However, without forming theSi₃N₄ film 21A, the SiON film 21B can be directly formed by nitridingthe surface of the silicon substrate 20 with N₂O gas before forming theHfO₂ film 22A.

[0111] In the process shown in FIG. 7B, hydrogen (H) contained in the Hfsource is spontaneously captured in the HfO₂ film 22A. On the otherhand, carbon (C) contained in the Hf source is oxidized by the O₂ gas asan oxidizing agent, so that it is exhausted in the form of CO or CO₂from the chamber. In the chamber, in addition to Hf, O, C, and H, whichare constituent elements of the Hf source, N₂ gas is present, but the N₂gas is very inert at temperatures below about 500° C., so that aninfluence of the N₂ gas can be ignored.

[0112] When the HfO₂ film 22A was analyzed by a SIMS method (secondaryion mass spectroscopy), it was found that primary elements constitutingthe HfO₂ film 22A were Hf and O. In the HfO₂ film 22A, 3×10¹⁹ to 4×10²⁰carbon atoms/cm³ and 5×10²⁰ to 4×10²¹ hydrogen atoms/cm³ were contained.

[0113] Next, a heat treatment (hereinafter, referred to as PDA (postdeposition anneal)) is performed with respect to the HfO₂ film 22A. PDAis performed, for example, in a nitrogen atmosphere at about 700° C. for30 seconds. Now, changes occurring in the stacked structure of the SiONfilm 21B and the HfO₂ film 22A by performing PDA will be described indetail with reference to FIGS. 9A to 9D. As described above, beforeperforming PDA, as shown in FIG. 9A, the SiON film 21B and the HfO₂ film22A contain hydrogen. When PDA is performed, as shown in FIG. 9B,hydrogen is desorbed from the SiON film 21B and the HfO₂ film 22Aefficiently in the form of hydrogen gas. As a result, as shown in FIG.9C, vacancies (white circles in FIG. 9C) are formed in the SiON film 21Band the HfO₂ film 22A. Then, as shown in FIG. 9D, silicon contained inthe silicon substrate 20 or the SiON film 21B is diffused into the HfO₀₂film 22A through the vacancies, and Hf contained in the HfO₂ film 22A isdiffused into the SiON film 21B. As a result, as shown in FIG. 7C, asilicon-containing HfO₂ film 22 having high thermal stability is formed,and a lower barrier film 21 made of the Hf-containing SiON film having ahigh relative dielectric constant can be formed. The silicon-containingHfO₂ film 22 is formed by making the HfO₂ film 22A dense by thediffusion of silicon. The specific composition of the lower barrier film21 is the same as the lower barrier film 11 b of the first embodiment.

[0114] In other words, vacancies obtained by desorbing hydrogen from theHfO₂ film 22A and the SiON film 21B has the effect of promoting mutualdiffusion of Hf and Si. In this case, setting the temperature for PDA toabout 700° C. brings about double effects, that is, an effect ofpromoting hydrogen desorption to facilitate formation of vacancies andan effect of facilitating diffusion of Hf or Si. As a result, one PDAallows Si to be captured in the HfO₂ film 22A to form thesilicon-containing HfO₂ film 22 having high thermal stability, andallows Hf to be captured in the SiON film 21B to form the lower barrierfilm 21 (Hf-containing SiON film) having a high relative dielectricconstant. Therefore, the thermal stability of a gate insulating film 25(see FIG. 8C) as a whole including the silicon-containing HfO₂ film 22and the lower barrier film 21 can be improved, and consequently therelative dielectric constant of the gate insulating film 25 as a wholecan be increased.

[0115] Next, the surface of the silicon-containing HfO₂ film 22 isnitrided lightly, so that as shown in FIG. 8A, an upper barrier film 23with a thickness of about 2 nm having a high relative dielectricconstant is formed. That is to say, the upper barrier film 23 is formedof the silicon-containing HfO₂ film containing nitrogen. The specificcomposition of the upper barrier film 23 is the same as that of theupper barrier film 11 c of the first embodiment.

[0116] Next, as shown in FIG. 8B, a polysilicon film 24 serving as agate electrode is formed on the upper barrier film 23 by, for example,CVD. Thereafter, the polysilicon film 24, the upper barrier film 23, thesilicon-containing HfO₂ film 22, and the lower barrier film 21 aredry-etched sequentially, using a mask pattern (not shown) covering agate electrode formation region. Thus, as shown in FIG. 8C, a gateelectrode 26 is formed on the silicon substrate 20 via the gateinsulating film 25 having a stacked structure of the lower barrier film21, the silicon-containing HfO₂ film 22, and the upper barrier film 23.Thereafter, ions are implanted into the silicon substrate 20 with thegate electrode 26 as a mask, so that an impurity diffusion layer 27serving as a source region or a drain region is formed. Finally, inorder to activate impurities in the impurity diffusion layers 27, a heattreatment is performed at about 950° C. for about 30 minutes. Theprocesses described above provide a MIS electric field effect transistorhaving the high-k gate insulating film.

[0117] As described above, according to the second embodiment, the HfO₂film 22A containing hydrogen is formed on the silicon substrate 20, andthen a heat treatment (PDA) is performed with respect to the HfO₂ film22A to desorb hydrogen, and silicon is diffused in the HfO₂ film 22Athrough the thus formed vacancies so that the silicon-containing HfO₂film 22 is formed. For this reason, it is possible to allow silicon tobe contained efficiently in the HfO₂ film 22A and the vacancieseventually disappear so that the silicon-containing HfO₂ film 22 becomesdense. In this case, as described in the first embodiment, thesilicon-containing HfO₂ film 22 is hardly crystallized by a hightemperature in the production process, so that the silicon-containingHfO₂ film 22 remains mostly amorphous even after a device is complete.As a result, leak current can be suppressed from occurring in the gateinsulating film 25 having the silicon-containing HfO₂ film 22, that is,the high-k gate insulating film. Therefore, the thermal stability of thehigh-k gate insulating film is improved, so that a semiconductor devicehaving excellent heat resistance can be realized and the process marginin the production of a semiconductor device can be increased.

[0118] Furthermore, according to the second embodiment, before formingthe HfO₂ film 22A, the Si₃N₄ film 21A containing hydrogen is formed onthe silicon substrate 20. The Si₃N₄ film 21A is oxidized when formingthe HfO₂ film 22A and turns into the SiON film 21B. Thereafter, when theHfO₂ film 22A is subjected to PDA, silicon contained in the SiON film21B is diffused into the HfO₂ film 22A. Moreover, hydrogen is desorbedfrom the SiON film 21B to form vacancies, and Hf contained in the HfO₂film 22A is diffused into the SiON film 21B through the vacancies, sothat the lower barrier film 21 is formed. Therefore, it is ensured thatsilicon can be contained in the HfO₂ film 22A. Furthermore, the HfO₂film 22A or the silicon-containing HfO₂ film 22 can be prevented frombeing reacted with the silicon substrate 20. Furthermore, the lowerbarrier film 21 contains the same metal, Hf as in the silicon-containingHfO₂ film 22, so that the relative dielectric constant of the lowerbarrier film 21 can be high, and thus the relative dielectric constantof the gate insulating film 25 as a whole can be high.

[0119] Moreover, according to the second embodiment, the upper barrierfilm 23 is formed by nitriding the surface of the silicon-containingHfO₂ film 22 in a process between the process for performing PDA to theHfO₂ film 22A and the process for forming the polysilicon film 24serving as the gate electrode 26. Therefore, the material of the gateelectrode 26 and material of the silicon-containing HfO₂ film 22 areprevented from diffusing each other. Furthermore, the upper barrier film23 contains the same metal, Hf as in the silicon-containing HfO₂ film22, so that the relative dielectric constant of the upper barrier film23 can be high, and thus the relative dielectric constant of the gateinsulating film 25 as a whole can be high.

[0120] Furthermore, according to the second embodiment, the HfO₂ film22A is formed by CVD that employs a source precursor containing hafniumand hydrogen, so that it is ensured that hydrogen can be contained inthe HfO₂ film 22A.

[0121] Hereinafter, the features (e.g., mutual diffusion of Hf and Si byhydrogen desorption) and the effect (e.g., improvement of thermalstability) of the process of performing PDA to the HfO₂ film 22A will bedescribed with reference to the drawings showing experiment data or thelike.

[0122]FIG. 10 shows the result of measurement by TDS (thermal desorptionspectroscopy) regarding hydrogen that is being desorbed from the HfO₂film by a heat treatment. In FIG. 10, the horizontal axis shows the heattreatment temperature and the vertical axis shows the spectrum intensityof hydrogen gas measured by TDS. As shown in FIG. 10, when the heattreatment temperature reaches about 400° C., first, hydrogen adsorbed onthe surface of the HfO₂ film starts to be desorbed. Thereafter, when theheat treatment temperature reaches about 700° C., hydrogen contained inthe HfO₂ film is desorbed. The density of hydrogen molecules that wascontained in the HfO₂ film just after deposition and eventually desorbedfrom the HfO₂ film by a heat treatment was measured and found to be ashigh as 5.6×10²⁰ molecules/cm². According to the results shown in FIG.10, when the heat treatment temperature is about 700° C., the detectedamount of desorbed hydrogen is largest. Therefore, the optimaltemperature for PDA is about 700° C., and the thus setting allowsexcessive hydrogen contained in the HfO₂ film to be desorbed so that theHfO₂ film can be made dense most effectively.

[0123] While performing a heat treatment (temperature increase rate of10° C./min) in an ultrahigh vacuum with respect to a sample of the HfO₂film formed on a Si substrate by CVD with Hf-t-butoxide, which is aliquid Hf source, the HfO₂ film that was being heated were subjected toin-situ observation to see its changes, using a high resolutioncross-sectional TEM (transmission electron microscope), and thefollowing was confirmed. At room temperature (immediately after the HfO₂film is formed), an interface layer (corresponding to the SiON film 21B)that contains a large number of Si atoms and a small number of Hf atomsis present on the Si substrate, and the HfO₂ layer that contains a smallnumber of Si atoms and a large number of Hf atoms is present on theinterface layer. Thereafter, as the temperature increases, in thetemperature range from 620° C. to 850° C., a mutual diffusion layer thatcontains a smaller number of Si atoms than that of the interface layerand a smaller number of Hf atoms than that of the HfO₂ layer evidentlystarts to appear between the interface layer and the HfO₂ layer.Finally, when a high temperature annealing is performed at 860° C., thetotal physical thickness of a stacked structure (corresponding to thesilicon-containing HfO₂ film 22) of the HfO₂ layer and the mutualdiffusion layer is larger than that of the HfO₂ layer at the time ofdeposition (room temperature). That is to say, the interface layer iscontracted by expansion of the mutual diffusion layer, and as a result,the relative dielectric constant of the entire Hf silicate stackedstructure including the interface layer becomes high.

[0124] In the case of regular PDA, the temperature increase rate is ashigh as 50° C./sec, and the retention period at a heat treatmenttemperature of about 700° C. is as short as 30 seconds, so that thethermal budget (thermal load) is much smaller than that from the in-situobservation during heating by the high resolution cross-sectional TEM.Therefore, oxidation of the Si substrate caused by PDA occurs only 1 nmor less, and the interface layer becomes very thin because of the mutualdiffusion of Si and Hf so that the final interface layer (correspondingto the lower barrier film 21) is about 0.5 nm. Thus, the relativedielectric constant of the entire Hf silicate stacked structureincluding the interface layer becomes high, and as a result, the EOT ofthe stacked structure as a whole becomes very small. In other words,forming the HfO₂ film by CVD employing a Hf source containing hydrogenis very advantageous as a method for forming a high-k gate insulatingfilm. On the other hand, a HfO₂ film is formed by CVD employing aregular Hf source free from hydrogen, and an in-situ observation duringheating is performed with respect to the HfO₂ film with the highresolution cross-sectional TEM. Then, it was found that mutual diffusionhardly occurred between the interface layer and the HfO₂ layer. As aresult, the thermal stability of the HfO₂ layer was not improved and therelative dielectric constant of the stacked structure of the interfacelayer and the HfO₂ layer was not increased.

[0125]FIG. 11 shows the results of C-V measurement after the heattreatment with respect to the HfO₂ film containing hydrogen formed byCVD employing Hf-t-butoxide. More specifically, annealing for activatingimpurities implanted to the gate electrode was performed at 900° C.,950° C. and 1050° C. with respect to samples of a MOS capacitoremploying a HfO₂ film having a physical thickness of 3.0 to 3.3 nm asthe gate insulating film and polysilicon as the gate electrode. Then, agate voltage Vg was applied with a voltage of 0 V set on the substrateside. In FIG. 11, the horizontal axis shows the gate voltage (Vg) andthe vertical axis shows the capacitance. ♦ shows the measured value ofthe capacitance when a heat treatment was performed at 900° C., ▪ showsthe measured value of the capacitance when a heat treatment wasperformed at 950° C., and ▴ shows the measured value of the capacitancewhen a heat treatment was performed at 1050° C.

[0126] As shown in FIG. 11, when the HfO₂ film containing hydrogenformed of Hf-t-butoxide is used, stable C-V curve is shown even if theannealing temperature for activation is increased, and the temperatureat which the sample can withstand as an ideal MOS capacitor is as highas 1050° C. or more. In other words, in the HfO₂ film containinghydrogen, as a result of occurrence of significant mutual diffusion ofHf and Si accompanied by hydrogen desorption caused by PDA, aSi-containing layer is present on the surface side of the HfO₂ film.Therefore, also when polysilicon is used as the gate electrode, as shownin FIG. 11, very stable heat resistance is exhibited at about 1050° C.

[0127]FIG. 12 shows the result of C-V measurement after a heat treatmentwith respect to a HfO₂ film free from hydrogen formed by CVD employing asource free from hydrogen, specifically, Hf-nitrato (Hf(NO₃)₄) as acomparative example. More specifically, annealing for activatingimpurities implanted to the gate electrode was performed at 900° C.,950° C. and 1150° C. with respect to samples of a MOS capacitoremploying a HfO₂ film having a physical thickness of 3.0 to 3.3 nm asthe gate insulating film and polysilicon as the gate electrode. Then, agate voltage Vg was applied with a voltage of 0 V set on the substrateside. In FIG. 12, the horizontal axis shows the gate voltage (Vg) andthe vertical axis shows the capacitance. ▪ shows the measured value ofthe capacitance when a heat treatment was performed at 900° C., ♦ showsthe measured value of the capacitance when a heat treatment wasperformed at 950° C., and ▴ shows the measured value of the capacitancewhen a heat treatment was performed at 1150° C.

[0128] As shown in FIG. 12, when the HfO₂ film free from hydrogen formedof Hf-nitrato is used, the temperature at which the sample can withstandas an ideal MOS capacitor is at most 900° C. Taking the results shown inboth FIGS. 11 and 12 into consideration, the thermal stability guaranteetemperature when the HfO₂ film containing hydrogen is used is 1050° C.or more, whereas the thermal stability guarantee temperature when theHfO₂ film free from hydrogen is used is about 900° C. In other words,using the HfO₂ film containing hydrogen improves the thermal stabilityguarantee temperature by 150° C. or more.

[0129]FIG. 13 shows the results of comparison in the thermal stabilitybetween the case where a HfO₂ film containing hydrogen was used and thecase where a HfO₂ film free from hydrogen was used in a MOS capacitorhaving a stacked structure of Si substrate/SiN film/HfO₂film/polysilicon film. More specifically, annealing for activation wasperformed at temperatures in the range from 900° C. to 1150° C. for 30seconds in a nitrogen atmosphere with respect to each MOS capacitorsample. Then, a gate voltage (VG) of −1.0 V was applied with a voltageof 0 V set on the substrate side, and leak current J_(G) was measured.The HfO₂ film containing hydrogen was formed of Hf-t-butoxide, and theHfO₂ film free from hydrogen was formed of a source free from hydrogen.In FIG. 13, the horizontal axis shows the activation annealingtemperature, and the vertical axis shows the leak current J_(G). ♦ showsthe measured value of the leak current J_(G) when a source free fromhydrogen is used, and □ shows the measured value of the leak currentJ_(G) when Hf-t-butoxide was used.

[0130] As shown in FIG. 13, when the HfO₂ film containing hydrogenformed of Hf-t-butoxide was used and the annealing temperature foractivation was increased, an increase of the leak current J_(G) could berestricted to only one order. On the other hand, in the case where theHfO₂ film free from hydrogen was used and the annealing temperature foractivation was increased, the leak current J_(G) was increased by aboutthree orders, that is, about 1000 times larger than in the case of theHfO₂ film containing hydrogen. In other words, using the HfO₂ filmcontaining hydrogen can reduce the defect production probability toabout {fraction (1/1000)} of that in the case where the HfO₂ film freefrom hydrogen.

[0131] Each of the HfO₂ film containing hydrogen and the HfO₂ film freefrom hydrogen was deposited on a silicon substrate to the same physicalthickness (3 nm), and the EOT of the HfO₂ film including the interfacelayer was measured. The results were as follows. The EOT was 1.1 nm whenthe HfO₂ film containing hydrogen was deposited, and the EOT was 1.6 nmwhen the HfO₂ film free from hydrogen was deposited. That is to say, therelative dielectric constant when the HfO₂ film containing hydrogen wasdeposited was about 1.46 times higher than that when the HfO₂ film freefrom hydrogen was deposited. This is caused by the fact that when theHfO₂ film containing hydrogen was deposited, Si and Hf are diffusedmutually between the interface layer and HfO₂ layer so that Hf iscontained in the interface layer, and consequently the relativedielectric constant in the interface layer portion is reducedsignificantly.

[0132] A HfO₂ film containing hydrogen having a thickness of 3.5 nm wasformed on a silicon substrate, and then a PDA treatment (800° C., 30seconds) was performed with respect to the HfO₂ film. Thereafter, Si, 0and Hf were measured from the surface side of the HfO₂ film by XPS(X-ray photoelectron spectroscopy) using MgKa radiation and thecomposition of the HfO₂ film after the PDA treatment was found to be 0.6for Hf, 0.49 for Si and 2.0 for O. It should be noted that sinceprimarily the surface of the HfO₂ film was observed for measurement bythe XPS technique, the detection depth was set to about 2 to 3 nm bydetecting photoelectrons having an escape angle of 57 degrees withrespect to the surface of the substrate. The results as described aboveindicate that in the HfO₂ film after the PDA treatment, Si has beendiffused up to the vicinity of the surface.

[0133]FIG. 14 shows the relationship between the physical thickness ofthe HfO₂ film immediately after being formed and the leak current aftera MOS capacitor was complete in the case where PDA was performed withrespect to the HfO₂ film (containing hydrogen), which is the insulatingfilm of the MOS capacitor. More specifically, after a HfO₂ filmcontaining hydrogen was formed by CVD, PDA was performed to the HfO₂film in a nitrogen atmosphere at pressure of about 60000 Pa (450 torr)at 800° C. for 30 seconds. Thereafter, a polysilicon film that was toserve as a gate electrode was deposited. Then, after ions were implantedinto the polysilicon film, annealing for activation is performed in anitrogen atmosphere at a pressure of about 110000 Pa (760 torr) at 900°C. for 30 seconds. Thereafter, a gate voltage (V_(G)) of −1.0 V wasapplied with 0 V on the substrate side, and the leak current J_(G) wasmeasured. The physical thickness of the HfO₂ film immediately afterbeing formed is measured by an ellipsometry method (polarizationmethod). For comparison, with respect to samples of MOS capacitorsobtained by omitting the process of performing PDA with respect to theHfO₂ film, the relationship between the physical thickness of the HfO₂film immediately after being formed and the leak current after the MOScapacitor was produced was investigated.

[0134] As shown in FIG. 14, when PDA is performed, a smaller leakcurrent J_(G) is achieved than when PDA is not performed. This seems tobe caused for the reason as follows: Si is diffused to the HfO₂ film bythe PDA, which prevents the HfO₂ film from being crystallized byannealing for activation, therefore the HfO₂ film in the finished MOScapacitor remains mostly amorphous, so that the gate leak current can besuppressed from increasing. Furthermore, it seems that the gate leakcurrent has been reduced also by the fact that a reaction between theelectrode material and the material of the high dielectric constant filmhas been suppressed by achieving a dense silicon-containing HfO₂ film.As shown in FIG. 14, the effect of suppressing the gate leak current inthe case where PDA is performed is exhibited more significantly as thephysical thickness of the HfO₂ film is smaller. The above results haveconfirmed that it is very important to provide a process of performingPDA (post deposition anneal) with respect to the high dielectricconstant film after the high dielectric constant film that will serve asa gate insulating film is deposited and before a gate electrode isformed in order to reduce the leak current effectively.

[0135] In the second embodiment, a polysilicon film 24 is used as thegate electrode 26, but a metal film can be used instead. For example,the surface of the silicon-containing HfO₂ film 22 is nitrided, and thena TiN film and an Al film that will serve as the gate electrode 26 maybe deposited sequentially by sputtering. Alternatively, after thesurface of the silicon-containing HfO₂ film 22 is nitrided, a Ta filmthat will serve as the gate electrode 26 may be deposited.Alternatively, a TiN film, a TaN film or the like may be depositedwithout nitriding the surface of the silicon-containing HfO₂ film 22. Inthis case, Si or Ge can be mixed with the Ti film, the TaN film or thelike. When a metal film is used as the gate electrode 26 as describedabove, after the metal film is formed, defects in the gate insulatingfilm 25 can be reduced further by further applying a heat treatment(PMA: post metalization anneal). When a C-V measurement is performedwith respect to the thus formed MOS structure, it is confirmed that theamount of the defects in the insulating film and the correspondinghysteresis are reduced. A temperature of 700° C. or more is effective asthe temperature of PMA. When annealing is performed in a gas containinghydrogen at 450° C. for about 30 minutes, the interface state in thegate insulating film 25 can be reduced.

[0136] In the second embodiment, a HfO₂ film is used as the highdielectric constant material constituting the gate insulating film 25,ZrO₂, TiO₂, Ta₂O₅, La₂O₃, CeO₂, Al₂O₃, or BST (barium strontium titaniumoxide) can be used instead. Alternatively, ternary oxide such asHf_(x)Al_(y)O₂, where x>0 and y>0) can be used. Alternatively, metalsilicate in which Si atoms are contained in metal oxide as describedabove can be used. In any case, the effect of mutual diffusion in thehigh dielectric constant film containing hydrogen can be realizedregardless of the composition or the constituent materials at the timeof the deposition of the high dielectric constant film.

[0137] In the second embodiment, the HfO₂ film 22A is deposited by CVDemploying Hf-t-butoxide, which is a liquid Hf source precursor. However,instead of this, when CVD is used, other Hf source precursors containinghydrogen and hafnium such as tetrakis diethylamido hafnium, (TDEAH:C₁₆H₄₀N₄Hf), tetrakis dimethylamino hafnium (TDMAH: C₁₆H₃₆HfO₄), ortetrakis 1-methoxy-2-methyl-2-propoxy hafnium (Hf(MMP)₄:Hf[OC(CH₃)₂CH₂OCH₃]₄) can be used. Alternatively, a HfO₂ film can beformed by CVD employing a solid Hf source precursor such as Hf-nitratoNO₃)₄) and a source gas containing hydrogen such as hydrogen gas.Alternatively, when PVD (physical vapor deposition) such as sputteringis used, a target containing hafnium can be used in an atmospherecontaining hydrogen. More specifically, a hafnium target can be used inan atmosphere containing oxygen gas and argon gas to which hydrogen gasis added, or a hafnium oxide target can be used in an atmospherecontaining argon gas to which hydrogen gas is added. Hydrogen gas isadded for hydrogen to be captured in the high dielectric constant film(HfO₂ film).

[0138] In the second embodiment, hydrogen is captured in the HfO₂ film22A or the Si₃N₄ film 21A as a predetermined substance (substance forvacancy formation), but instead of this, for example, chlorine,fluorine, or iodine can be captured using a halogen-based gas. Anysubstances can be used as the substance for vacancy formation, as longas it can be desorbed from the HfO₂ film 22A or the Si₃N₄ film 21A inthe form of gas at a temperature of about 600 to 850° C. and can promotethe diffusion of Hf or Si through the thus formed vacancies.Furthermore, the substance for vacancy formation for the HfO₂ film 22Amay be different from that for the Si₃N₄ film 21A.

[0139] In the second embodiment, the Si₃N₄ film 21A, that is, the lowerbarrier film 21 can be formed by performing, for example, thermalnitridation or plasma nitridation in a gas containing nitrogen withrespect to the silicon substrate 20. Alternatively, the SiON film 21Bcan be directly formed by nitriding the surface of the silicon substrate20 with N₂O gas before forming the HfO₂ film 22A without forming theSi₃N₄ film 21A. Alternatively, the high dielectric insulating filmcontaining nitrogen that will become the lower barrier film 21 can bedirectly formed on the silicon substrate 20 by introducing a gascontaining nitrogen in the early stage of the formation of the HfO₂ film22A by evaporation.

[0140] In the second embodiment, the upper barrier film 23 can be formedby performing, for example, thermal nitridation or plasma nitridation ina gas containing nitrogen with respect to the silicon-containing HfO₂film 22. Alternatively, the upper barrier film 23 can be formed bynitriding the surface of the silicon-containing HfO₂ film 22 byintroducing nitrogen gas in the early stage of the formation of thepolysilicon film 24 that will serve as the gate electrode 26.Alternatively, the high dielectric insulating film containing nitrogenthat will become the upper barrier film 23 can be formed on the side ofthe surface of the HfO₂ film 22A by introducing a gas containingnitrogen in the final stage of the formation of the HfO₂ film 22A byevaporation.

[0141] In the second embodiment, PDA is performed with respect to theHfO₂ film 22A to form the silicon-containing HfO₂ film 22, and then theupper barrier film 23 is formed by nitriding the surface of thesilicon-containing HfO₂ film 22. However, instead of this, after theupper barrier film 23 is formed by nitriding the surface of the HfO₂film 22A, PDA is performed with respect to the HfO₂ film 22A to form thesilicon-containing HfO₂ film 22.

[0142] In the second embodiment, the entire stacked structure of thelower barrier film 21, the silicon-containing HfO₂ film 22 and the upperbarrier film 23 may contain nitrogen.

[0143] In the second embodiment, it is preferable that in the processshown in FIG. 7B, first, a source such as evaporated Hf-t-butoxide issupplied into a chamber, and then oxygen gas is supplied to the chamber,and thereafter the temperature in the chamber is increased from roomtemperature and kept in a predetermined temperature range of about 300to 500° C. This makes it possible that Hf molecules are adsorbed rapidlyon the silicon substrate 20 at a low temperature, so that the HfO₂ film22A can be formed uniformly. Furthermore, the incubation time from thestart of the supply of the source gas to the start of crystal growth ofthe HfO₂ film can be shortened. Furthermore, the interface layer (SiONfilm 21B) formed between the HfO₂ film 22A and the silicon substrate 20can be thin.

[0144] In the second embodiment, it is preferable that the temperaturefor the heat treatment in PDA in the process shown in FIG. 7C is 600° C.or more and 850° C. or less. This ensures that hydrogen can be desorbedfrom the HfO₂ film 22A and thus silicon can be diffused in the HfO₂ film22A.

[0145] In the second embodiment, it is preferable to satisfyT≦6.69·y/(x+y)+749.4, where the composition of the silicon-containingHfO₂ film 22 is expressed as Hf_(x)Si_(y)O, where x>0, and y>0, and themaximum temperature in the production process is expressed as T [° C.].This ensures the thermal stability of the gate insulating film 25 havingthe silicon-containing HfO₂ film 22. When the gate electrode 26 is madeof a material containing silicon, it is preferable to satisfyT≦6.69·y/(x+y)+749.4, and y/(x+y)≦0.30. This ensures the thermalstability and the reliability of the gate insulating film 25 having thesilicon-containing HfO₂ film 22.

[0146] The invention may be embodied in other forms without departingfrom the spirit or essential characteristics thereof. The embodimentsdisclosed in this application are to be considered in all respects asillustrative and not limiting. The scope of the invention is indicatedby the appended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are intended to be embraced therein.

What is claimed is:
 1. A semiconductor device comprising: a gateinsulating film formed on a substrate; and a gate electrode formed onthe gate insulating film; the gate insulating film comprising: a highdielectric constant film containing a metal, oxygen and silicon; and alower barrier film formed below the high dielectric constant film andcontaining the metal, oxygen, silicon and nitrogen.
 2. The semiconductordevice according to claim 1, wherein the gate insulating film comprisesan upper barrier film formed above the high dielectric constant film,and the upper barrier film contains the metal, oxygen and nitrogen. 3.The semiconductor device according to claim 1, wherein 0.23≦y/(x+y)≦0.90when a composition of the high dielectric constant film is expressed asM_(x)Si_(y)O, where M, O and Si represent the metal, oxygen and silicon,respectively, and x>0 and y>0.
 4. The semiconductor device according toclaim 1, wherein 0.23≦y/(x+y)≦0.30 when a composition of the highdielectric constant film is expressed as M_(x)Si_(y)O, where M, O and Sirepresent the metal, oxygen and silicon, respectively, and x>0 and y>0.5. The semiconductor device according to claim 1, wherein x/(x+y)≧0.10when the metal is hafnium or zirconium, and a composition of the lowerbarrier film is expressed as M_(x)Si_(y)ON, where M, O, Si and Nrepresent the metal, oxygen, silicon and nitrogen, respectively, and x>0and y>0.
 6. The semiconductor device according to claim 1, wherein thegate electrode is a metal gate electrode.
 7. A method for producing asemiconductor device comprising the steps of: forming a high dielectricconstant film containing a metal, oxygen and a predetermine substance ona substrate; performing a heat treatment with respect to the highdielectric constant film to diffuse silicon from the side of thesubstrate into the high dielectric constant film, thereby forming asilicon-containing high dielectric constant film; and forming aconductive film for serving as a gate electrode on thesilicon-containing high dielectric constant film.
 8. The method forproducing a semiconductor device according to claim 7, wherein thepredetermined substance is hydrogen.
 9. The method for producing asemiconductor device according to claim 7, wherein the metal is hafniumor zirconium.
 10. The method for producing a semiconductor deviceaccording to claim 7, comprising forming an insulating film containingsilicon, nitrogen and the predetermined substance on the substratebefore the step of forming the high dielectric constant film; andwherein the step of performing a heat treatment with respect to the highdielectric constant film comprises diffusing silicon contained in theinsulating film into the high dielectric constant film, and forming alower barrier film by diffusing the metal contained in the highdielectric constant film into the insulating film.
 11. The method forproducing a semiconductor device according to claim 7, wherein the stepof forming the high dielectric constant film comprises forming the highdielectric constant film by CVD employing a source precursor containingthe metal and the predetermined substance.
 12. The method for producinga semiconductor device according to claim 7, wherein the step of formingthe high dielectric constant film comprises forming the high dielectricconstant film by CVD employing a source precursor containing the metaland a source gas containing the predetermined substance.
 13. The methodfor producing a semiconductor device according to claim 7, wherein thestep of forming the high dielectric constant film comprises forming thehigh dielectric constant film by PVD employing a target containing themetal in an atmosphere containing the predetermined substance.
 14. Themethod for producing a semiconductor device according to claim 7,comprising the step of forming an upper barrier by nitriding a surfaceof the silicon-containing high dielectric constant film between the stepof performing a heat treatment with respect to the high dielectricconstant film and the step of forming a conductive film.
 15. The methodfor producing a semiconductor device according to claim 7, comprisingthe step of forming an upper barrier by nitriding a surface of the highdielectric constant film between the step of forming a high dielectricconstant film and the step of performing a heat treatment with respectto the high dielectric constant film.
 16. The method for producing asemiconductor device according to claim 7, wherein a temperature for theheat treatment in the step of performing the heat treatment with respectto the high dielectric constant film is 600° C. or more and 850° C. orless.
 17. The method for producing a semiconductor device according toclaim 7, wherein T≦6.69·y/(x+y)+749.4, when a composition of thesilicon-containing high dielectric constant film is expressed asM_(x)Si_(y)O, where M, O and Si represent the metal, oxygen and silicon,respectively, and x>0 and y>0, and a maximum temperature in a productionprocess is expressed as T [° C.].
 18. The method for producing asemiconductor device according to claim 17, wherein the gate electrodeis made of a material containing silicon, and y/(x+y)≦0.30.
 19. Themethod for producing a semiconductor device according to claim 7,wherein the gate electrode is a metal gate electrode, the methodcomprising the step of performing a heat treatment with respect to thesubstrate after the step of forming a conductive film.
 20. A method forproducing a semiconductor device comprising the steps of: forming a highdielectric constant film containing a metal, oxygen and hydrogen on asubstrate; performing a heat treatment with respect to the highdielectric constant film to diffuse silicon from the side of thesubstrate into the high dielectric constant film, thereby forming asilicon-containing high dielectric constant film; and forming aconductive film for serving as a gate electrode on thesilicon-containing high dielectric constant film.
 21. The method forproducing a semiconductor device according to claim 20, wherein themetal is hafnium or zirconium.
 22. The method for producing asemiconductor device according to claim 20, comprising forming aninsulating film containing silicon, nitrogen and hydrogen on thesubstrate before the step of forming the high dielectric constant film;and wherein the step of performing a heat treatment with respect to thehigh dielectric constant film comprises diffusing silicon contained inthe insulating film into the high dielectric constant film, and forminga lower barrier film by diffusing the metal contained in the highdielectric constant film into the insulating film.
 23. The method forproducing a semiconductor device according to claim 20, wherein the stepof forming the high dielectric constant film comprises forming the highdielectric constant film by CVD employing a source precursor containingthe metal and hydrogen.
 24. The method for producing a semiconductordevice according to claim 20, wherein the step of forming the highdielectric constant film comprises forming the high dielectric constantfilm by CVD employing a source precursor containing the metal and asource gas containing hydrogen.
 25. The method for producing asemiconductor device according to claim 20, wherein the step of formingthe high dielectric constant film comprises forming the high dielectricconstant film by PVD employing a target containing the metal in anatmosphere containing hydrogen.
 26. The method for producing asemiconductor device according to claim 20, comprising the step offorming an upper barrier by nitriding a surface of thesilicon-containing high dielectric constant film between the step ofperforming a heat treatment with respect to the high dielectric constantfilm and the step of forming a conductive film.
 27. The method forproducing a semiconductor device according to claim 20, comprising thestep of forming an upper barrier by nitriding a surface of the highdielectric constant film between the step of forming a high dielectricconstant film and the step of performing a heat treatment with respectto the high dielectric constant film.
 28. The method for producing asemiconductor device according to claim 20, wherein a temperature forthe heat treatment in the step of performing the heat treatment withrespect to the high dielectric constant film is 600° C. or more and 850°C. or less.
 29. The method for producing a semiconductor deviceaccording to claim 20, wherein T≦6.69·y/(x+y)+749.4, when a compositionof the silicon-containing high dielectric constant film is expressed asM_(x)Si_(y)O, where M, O and Si represent the metal, oxygen and silicon,respectively, and x>0 and y>0, and a maximum temperature in a productionprocess is expressed as T [° C.].
 30. The method for producing asemiconductor device according to claim 29, wherein the gate electrodeis made of a material containing silicon, and y/(x+y)≦0.30.
 31. Themethod for producing a semiconductor device according to claim 20,wherein the gate electrode is a metal gate electrode, and the methodcomprising the step of performing a heat treatment with respect to thesubstrate after the step of forming a conductive film.